Different response of plastic film mulching on greenhouse gas intensity (GHGI) between chemical and organic fertilization in maize upland soil.

Since plastic film mulching (PFM) can deplete soil organic carbon (SOC) stock but increase greenhouse gas (GHG) emissions, PFM utilization is still debating. To determine the influence of PFM on global warming, PFM and no-mulching treatments were installed under chemical and organic fertilizations. In organic fertilization, cover crop was cultivated during the fallow season, and its biomass was incorporated as green manure. To estimate net global warming potential (GWP), two GHG (N2O and CH4) fluxes and SOC stock changes were determined. SOC stock changes were estimated using net ecosystem carbon budget (NECB), which implies the difference between C input and output. GHG intensity (GHGI) was calculated using net GWP per unit of grain yield. PFM increased maize grain yields by approximately 45-95% over no-mulching under the same fertilization, but it was more effective in organic fertilization, due to higher nutrient input. In contrast, PFM increased seasonal N2O and CH4 emissions by 5-10% and 130-260% over no-mulching under the same amendment, respectively. Compared with no-mulching, PFM decreased more highly SOC stock in organic fertilization (around 140-200%) than chemical fertilization (20-30%), due to higher harvest removal and respired C loss. Irrespective with fertilization and mulching background, net GWP was decided by SOC stock change, which covered about 75-90% of net GWP, and then followed by N2O. PFM differently influenced net GWP and GHGI between chemical and organic fertilizations. In chemical fertilization, PFM increased net GWP by 20-30% over no-mulching, but decreased GHGI by 25-35%. However, in organic amendment, PFM highly increased net GWP and GHGI by approximately 115-160% and 30-80% over no-mulching, respectively. PFM in chemical fertilization could be very powerful tool to decrease GHGI via crop yield increase. However, in organic farming, PFM should be carefully selected to increase crop yields, due to more highly increased global warming impact.